The goal of the proposed project is to maintain and expand a specific-pathogen free (SPF) breeding colony of pigtail macaques (Macaca nemestrina) for the support of NlH-supported research at the Washington National Primate Research Center (WaNPRC). Macaques are a valuable model of human disease and are an essential resource for biomedical research. M. nemestrina possess unique characteristics that make them invaluable, particularly in the study of AIDS pathogenesis, immunology, vaccine development, and vaginal microbicide evaluation. The WaNPRC maintains the only major domestic breeding colony of M. nemestrina. In order to meet the demand for M. nemestrina at the WaNPRC in recent years, it has been necessary to import animals from Indonesia. Even with the importation, it has been a challenge to meet requests for animals for NlH-supported research. We propose over the course of the next four years to expand our domestic SPF breeding colony to a self-sustaining census of 1400 animals which will meet the anticipated demand for M. nemestrina. We will employ two major strategies to meet this demand: Improved management, and importation of breeding animals. M. nemestrina are not as hardy as other macaque species, and have different breeding requirements. We have recently established a breeding facility for M. nemestrina in Arizona that is directly managed by the WaNPRC, and focuses specifically on that species. We anticipate that with this strategy we will be able to reduce mortality and increase fertility, resulting in a net increase in the number of animals in th colony. We will also import a total of 200 M. nemestrina to reach our goal of colony expansion. We will have imported animals tested serologically for viral antibodies prior to shipment and confirm their pathogen-free status with in-house repeated serologic testing. Viral pathogens that interfere with research results (SIV, STLV, SRV) or are a zoonotic risk to humans (McHV-1, also known as herpes B) will be eliminated from the colony by raising uninfected offspring separately from infected progenitors and testing all animals in the colony regularly.